Understanding WACC and Discount Rates

Learn how to calculate weighted average cost of capital and why it matters for your valuation. We break down the components and show you how to apply them in your model without getting lost in theory.

9 min read Intermediate July 2026

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DCF Mastery Editorial Team

Editorial Team

Why WACC Matters More Than You Think

Here's the thing: your DCF model is only as good as the discount rate you use. Get it wrong, and your entire valuation falls apart. WACC — weighted average cost of capital — is the bridge between what a company is worth and how you calculate it.

Think of it this way. Every dollar your company uses comes from somewhere: debt (bonds, bank loans) or equity (shareholders). Each source has a cost. Debt holders want interest payments. Equity investors want returns. WACC blends these costs together, weighted by how much of each the company uses.

Financial analyst reviewing WACC calculation on spreadsheet at desk, multiple monitors showing data

Breaking Down WACC Into Components

WACC has two main moving parts: cost of equity and cost of debt. You'll see the formula written as:

WACC = (E/V Cost of Equity) + (D/V Cost of Debt (1 - Tax Rate))

Where E is equity value, D is debt value, and V is total value. That tax adjustment on the debt side? That's because interest payments are tax-deductible. So debt's actually cheaper than it looks at first glance.

Cost of equity is trickier to calculate than cost of debt. You can't just look it up in an annual report. Most people use the Capital Asset Pricing Model — CAPM — which ties expected returns to how risky the stock is relative to the overall market.

Key Numbers You'll Need

Risk-Free Rate

Usually the yield on a 10-year government bond. In Canada, that's the Government of Canada 10-year bond. This is what investors could earn without any risk, so it's your starting point for cost of equity.

Beta

A measure of how much the stock bounces around compared to the overall market. A beta of 1.0 means it moves with the market. Above 1.0 means it's more volatile — riskier. You'll find beta on Yahoo Finance, Bloomberg, or calculate it yourself from historical returns.

Market Risk Premium

The extra return investors expect for taking on stock market risk versus holding safe government bonds. Historically around 5-7% in North America. This isn't something you look up — it's an assumption you make, and different analysts argue about it constantly.

Cost of Debt

The interest rate the company pays on its borrowings. Look at the company's debt footnotes in the annual report. If it has multiple loans or bonds at different rates, take a weighted average. Don't forget the tax adjustment — that's where the real savings come in.

Excel spreadsheet with WACC calculation showing cost of equity and debt components side by side

Building WACC Into Your Model

When you're actually building a DCF in Excel, you'll create a WACC calculation section at the top. Start with your inputs — risk-free rate, beta, market risk premium, cost of debt, tax rate, and the capital structure (how much equity vs. debt the company has).

Then calculate cost of equity using CAPM: Risk-Free Rate + (Beta Market Risk Premium). Add in your cost of debt adjusted for taxes. Blend them together using the weights. That's your WACC.

Use that single number as your discount rate for all future cash flows. It's the rate you apply when you're converting future cash flows into today's dollars. Most analysts use the same WACC for years 1-5 and adjust it slightly for terminal value if they think the risk profile changes.

Important Note

This guide is educational material designed to help you understand WACC concepts and DCF methodology. It's not financial advice, and the specific calculations or assumptions shouldn't be used for real investment decisions without consulting with a qualified financial professional. Market conditions, company circumstances, and economic assumptions change — what works in your model depends on your specific situation and the accuracy of your inputs.

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Building Your First DCF Model in Excel

Walk through creating a complete DCF spreadsheet from scratch, including revenue projections, expense assumptions, and working capital changes.

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Terminal Value Calculation Methods

Terminal value often represents most of your enterprise value. We cover both the perpetuity growth method and exit multiple approach.

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Sensitivity Analysis and Scenario Testing

See how changing your key assumptions affects valuation. This guide shows you how to stress-test your model and present multiple outcomes.

Making WACC Work for You

WACC isn't complicated once you break it down into pieces. You're really just answering one question: What return do investors need to justify putting money into this company? Debt investors want interest. Equity investors want appreciation. WACC blends both together.

The challenge isn't the math — it's getting the inputs right. Spend time thinking about your cost of equity assumptions. Is 7% market risk premium reasonable for this industry? Does the beta feel right? Is the debt cost accurate? Small changes in these inputs create big changes in your valuation, so it's worth getting them solid.

Start building your WACC calculation into a separate section of your model. Keep it clean and documented. You'll reference it constantly, and you'll want to be able to explain every number if someone challenges your work. That's how you build credibility with your analysis.

Ready to put this into practice?

Explore Our DCF Building Guide